Better hygiene and sanitation is the actual reason for the decreased infections, not vaccines

While it is true that better sanitation and hygiene also reduce rates of infection it is relatively easy to isolate the effects of both. One example is measles, when the measles vaccine was introduced in 1963 there was a steady infection rate in the United States of about 400,000 case a year. While sanitation and hygiene did not appreciably change in the next decade in the U.S., the infection rate plummeted to less than 25,000 cases in 1970. There is also the rate of HiB infections which had an incidence rate of 20,000 in 1990, and then after the introduction of the vaccine in 1993 the incidence rate was 1,500 (3). which when the Another example is polio where the rate of infection went from about 35,000 cases a year in the decade after World War II in the United States to zero by 1979 with the introduction of the vaccine in 1953 (1).

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¹Polio Elimination in the United States (25 October 2019), retrieved 2 May 2020, https://www.cdc.gov/polio/what-is-polio/polio-us.html

²Studio, E. (n.d.). 'Cleaning Elements' by Eucalyp Studio. Retrieved May 4, 2020, from https://www.iconfinder.com/icons/3460330/clean_hand_sanitation_wash_icon 

³Vaccines Myths Debunked (2020), retrieved 2 May 2020, https://www.publichealth.org/public-awareness/understanding-vaccines/vaccine-myths-debunked/